dsh-sidebar-flex: Get back vertical space for the DSH sidebar session list

In the sidebar of the DSH client GUI, the global panel list is fixed and non-scrolling, consuming approximately 396px, leaving only about 120–140px for the workspace/session area. This causes long session lists to be clipped, making it impossible to click on target sessions, as the shell does not provide a mechanism to swap the heights of the top and bottom sections. dsh-sidebar-flex (maintained by yuyu121704, client category) adds a 10px divider bar below the panel list: dragging up or down compresses the panel list and yields the height to the session list; double-clicking or right-clicking restores the natural height; using arrow keys to fine-tune by 24px when focused; the height is stored in localStorage and restored after reload. The panel list has a minimum height of 54px; when compressed below its natural height, it is scrollable without discarding content. The plugin only adjusts the height, not the sidebar width, and does not interfere with the session content column. The client side polls the sidebar column, writes an inline height, and uses MutationObserver to handle React re-rendering, while the host side deliberately leaves the area empty. Installation requires manually creating a junction or copying and registering the file into the profile's `dsh.profile.bundles`, rather than via a package manager. It is compatible with peerDependencies `@deepseek-ai/dsh >=0.2.0-rc.2 <0.3.0-0`, version 0.2.2, and has an MIT license.